Certain water heater appliances include a sealed system for heating water within a tank of the water heater appliance. The sealed systems generally include an evaporator. The evaporator may be formed from a variety of metals, such as copper and/or aluminum. Previously, certain evaporator components were formed with copper. However, with recent copper price increases, aluminum frequently replaces copper in such evaporator components in order to avoid the price increases.
Incorporating aluminum into evaporator components poses certain challenges. For example, joining aluminum components to copper components within the sealed system can be difficult and expensive due to the different material properties of the metals. Transitioning between copper tubing and aluminum evaporator component can be done with several methods including brazing, mechanical clinching and resistive autogenous fusion or welding. Brazing involves the use of costly filler metals and fluxes and mechanical clinching may provide a less reliable joint. Resistive autogenous fusion or welding can be inexpensive and provide a reliable joint. However, maintaining consistent process parameters during resistive autogenous fusion or welding in order to provide a suitable bond between copper tubing and aluminum evaporator components is difficult. When the process parameters are inconsistent, the bond may be undersized, brittle and not fully bonded thus resulting in unreliable joints.
According, a method for joining copper and aluminum components that assists with provides a reliable bond between the copper and aluminum components would be useful. In particular, a method for joining copper and aluminum tubing within an evaporator that assists with provides a reliable bond between the copper and aluminum tubing would be useful.